Subtract 7 from the NRR rating to get the actual optimal noise reduction value.Measure the environment using an SPL meter using the A-weighted setting, slow response.Rather than subtract the NRR rating from the measured environment dBA SPL, you need to do the following: Unfortunately, the math isn’t as straightforward as you might think…which is min-numbingly frustrating. That number tells you how you can calculate how many decibels are reduced by proper wearing of the device. It actually lets us work in these environments for longer! With hearing protection, you can work for more hours in environments where you might otherwise be constrained-and you can do so without violating those OSHA limits! When looking for hearing protection, check out the NRR rating. The purpose of hearing protection isn’t just to protect our ears. You only have one set of ears! NRR Ratings and Hearing Protection You also cannot (legally or permissibly) exceed these time thresholds (nor should you want to). You can also work for just 1 hour in an environment with 105 decibels of noise.
For example, you can work for 8 hours in a 90 dBA SPL environment. OSHA specifically governs just how much noise (in dBA) you can be exposed to per day. OSHA Table G-16 Permissible Noise Exposure How Sound Pressure Level and the Decibel Scale Affect Work You typically see C-weighted measurements designated as dBC or dB(C). You typically see C-weighting used when measuring bass frequencies is a big part of the equation. Most SPL meters include both A-weighted and C-weighted modes (as well as fast and slow response modes to get more of an average SPL vs an instantaneous reading). The reason for C-weighting is to more accurately reproduce how the human ear hears at higher output levels (like 100 dB SPL) where we tend to experience a much flatter response. You express A-weighted sound pressure level measurements by designating dBA or dB(A) SPL. Similar to the human ear, A-weighting rounds off both lower and higher frequencies that average people simply can’t hear. A Weighting – dBA SPLīy far, A-weighting is the most common type of measurement used in recording audio levels when it comes to noise. It has to do with how the sound pressure level meter records sound at various frequencies. If this were a home theater review website, we’d likely use dB(C) SPL, or C-weighted numbers. That simply means we’re using an A-weighted SPL reading. You may see OPE Reviews and others list 88 dB(A) SPL or 88 dBA SPL. What’s the Deal with A-Weighted vs C-Weighted dB SPL? So, let’s go back to our initial 60 dB conversation… Another conversation measuring: In case you’re wondering-your vacuum cleaner might be that loud! Your ears can begin taking damage starting around 85 dB(A) with prolonged exposure. Keep in mind that as you go up the dB(A) chart, both your perception of sound as well as the actual SPL increases. Below we’ve included one of our favorites. You can find any number of decibel-equivalent examples that help in understanding how loud real world situations are to the human ear. Secondly, we need to understand how SPL affects just how loud something sounds. First, we need to understand that we can measure the actualsound pressure level. We need to keep two things straight when dealing with matters pertaining to the dB scale. Sound Pressure Level and the Decibel Scale For example, we have a lot of testing data and science that lets us know what levels of sound pressure can be sustained safely over various periods of time. Taking that data we can do some amazing things-like calculate ways to prevent hearing loss. Why are we talking about sound pressure levels and decibels? Well, for one, they give us the very numerical scale we use when referring to how loud something is. For the most part, we’re talking about air-and we assume 0 atmospheres (even though that’s not quite accurate). OK, fine-but what IS sound pressure level? SPL measures the difference between the pressure from a sound wave vs the pressure of what it’s traveling through. While it natively uses Pascals (Pa) as a unit of measurement, we use devices that automatically convert that into the more commonly-used decibel (dB) scale. SPL or sound pressure level-in a nutshell-is a measurement of sound pressure. Keeping all that in mind, we assembled a quick article that covers both sound pressure level (SPL) and the decibel scale (or dB scale) in depth. Similarly, most don’t understand the decibel or dB scale either. In particular, we get the what is sound pressure level question almost monthly. While the gas vs battery lawn mower debate heats up and results in less noise pollution, many still have questions. Any time you see a landscape crew, they have over-the-ear earmuffs or other hearing protection (like the ISOtunes Link) to guard against noise. We talk a lot about hearing protection on the jobsite.